1. Field of the Invention
The present invention relates in general to electrochromic devices and, more particularly, to electrochromic polyelectrolyte gel mediums, for use in electrochromic devices, having improved creep resistance.
2. Background Art
Electrochromic devices have been known in the art for several years. While the utilization of electrochromic devices, such as electrochromic mirrors, windows, and transparencies has become increasingly popular, for example, among the automotive and aerospace industries, maintaining substantially uniform cell spacing between device substrates remains difficult for certain device configurations, including, but not limited to, large area device configurations. Without being bound to any one particular theory, it is believed that this uniformity change is due in part to a redistribution of the electrochromic device's solvent in the gel medium under the influence of the earth's gravitational force over time. One proposed solution to maintaining substantially uniform cell spacing between substrates has been to increase the amount of network polymer in the gel relative to the solvent in the electrochromic medium. However, this solution can lead to other problems, such as adversely affecting device coloring and/or clearing time, increasing the frequency and magnitude of undesirable thermally induced defects in the electrochromic medium, as well as increasing manufacturing time and difficulty and, in turn, cost.
It has been discovered that selective utilization of creep resistant crosslinked polyelectrolyte gel matrices enable an associated device to maintain substantially uniform cell spacing between device substrates without the above-identified drawbacks associated with increasing the concentration of the polymer network relative to the solvent in the electrochromic medium.
It is therefore an object of the present invention to provide an electrochromic medium for use in an electrochromic device having a crosslinked polyelectrolyte gel matrix with increased creep resistance that improves upon and/or remedies the aforementioned detriments and/or complications associated with the use of conventional electrochromic mediums.
These and other objects of the present invention will become apparent in light of the present specification, claims, and appended drawings.